Framework Seeks Balance Between Ambitious Target and Flexibility

WASHINGTON-The Environmental Protection Agency on Monday released a draft rule to regulate carbon emissions from hundreds of fossil-fired power plants across the U.S., the cornerstone of President Barack Obama's climate-change agenda. The proposed rule mandates that power plants cut U.S. carbon-dioxide emissions 30% by 2030 from levels seen in 2005, an aggressive target that marks the first attempt at limiting such pollution.

"That's like canceling out annual carbon pollution from two thirds of all cars and trucks in...